Directional coupler for transmission lines

ABSTRACT

A directional coupler for detecting and measuring unidirectional wave signals propagated along a transmission line. The coupler includes an insulative board, having a first layer of conductive material secured to one of the faces of the insulative board and a second layer of conductive material secured to the other face of the insulative board to define a predetermined impedance with respect to a ground plane partition member. A coupling element comprising a third layer of conductive material is also secured to the other face of the insulative board to define a predetermined impedance with respect to the second layer of conductive material. The ground plane partition member and the second layer of conductive material serve as a section of the transmission line. The coupling element is connected to a signal measuring network for developing an output signal having a value representative of the value of an unidirectional wave signal propagated along the transmission line. The assembly including the insulative board and plural conductive layers is mounted in a housing, and the partition member is electrically bonded to four of the side walls of the housing in order to define a pair of chambers within the housing and serves the function of substantially preventing the passage of electrical fields between these chambers.

United States Patent [191 Stevens DIRECTIONAL COUPLER FOR TRANSMISSIONLINES [75] Inventor: Harold E. Stevens,.Lyndhurst, Ohio [73] Assignee:Coaxial Dynamics, Inc.,Cuyahoga,

Ohio

22 Filed: Oct. 26, 1971 21 Appl.No.: 192,529

[52] US. Cl. 324/95, 333/10 1971; pg. 41-52. Fisher et a1.; UHFDirectional QST; Sept. 1970; pg. 26-31.

Primary ExaminerAlfred E. Smith Assistant ExaminerErnest F. KarlsenAttorney, Agent, or Firm-Watts, l-loffmann, Fisher & l-leinke Co.

[ 1 Aug. 13, 1974 [5 7] ABSTRACT A directional coupler for detecting andmeasuring unidirectional wave signals propagated along a transmissionline. The coupler includes an insulative board, having a first layer ofconductive material secured to one of the faces of the insulative boardand a second layer of conductive material secured to the other face ofthe insulative board to define a predetermined impedance with respect toa ground plane partition member. A coupling element comprising a thirdlayer of conductive material is also secured to the other face of theinsulative board to define a predetermined impedance with respect to thesecond layer of conductive material. The ground plane partition memberand the second layer of conductive material serve as a section of thetransmission line. The coupling element is connected to a signalmeasuring network for developing an output signal having a valuerepresentative of the value of an unidirectional wave signal propagatedalong the transmission line. The assembly including the insulative boardand plural conductive layers is mounted in a housing, and the partitionmember is electrically bonded to four of the side walls of the housingin order to define a pair of chambers within the housing and serves thefunction of substantially preventing the passage of electrical fieldsbetween these chambers.

6 Claims, 7 Drawing Figures l 35 ll L I i 2 l 58 :5 3

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' sum aor a DIRECTIONAL COUPLER FOR TRANSMISSION I LINES BACKGROUND OFTHE INVENTION This invention pertains to the art of electrical devicesfor detecting and measuring wave signals propagated along a transmissionline, and more particularly, to directional couples for measuringunidirectional radiofrequency wave signals on a transmission line.

In the operation of radio-frequency transmitting equipment, it isfrequently necessary to measure radiofrequency wave signals propagatedalong a transmission line. The data obtained by such measurements may beutilized to compute the standing-wave ratio of the transmission line,forward power propagated along the transmission line, reflected powerpropagated along the transmission line, et cetera.

Directional couplers have become an important component of transmittingsystems. These couplers have been utilized in conjunction withelectronic control circuitry for continuously monitoring forward andreflected power on a transmission line and for automati cally reducingthe input power to a transmitter when the forward or reflected power onthe transmission line exceeds a predetermined level.

Various electronic instruments have been employed to monitor and measurewave signals propagated along transmission lines. These instruments haveincluded various types of coupler arrangements and configurationsbetween a primary transmission line and secondary line, or couplingcircuit. For example, capacitative coupling circuits, inductive couplingcircuits, and resistive bridge networks have been employed eitherseparately, or in various combinations, to transfer a portion of theenergy on a primary transmission line to a secondary line formeasurement.

These conventional directional couplers have generally comprised asection of coaxial transmission line which is machined in a cylindricalconfiguration from metal. Normally, inductive and capacitive elementsextend through slotted apertures in the side walls of the couplers forconnecting a signal measuring network to the transmission line. Thecoupling elements generally take the form of wire coils and capacitiveprobes which are supported at one end, and extend into and intercept anelectrical field which exists between the center conductor and the outerconductor of the coaxial transmission line. One example of this type ofcoupler is that shown in conjunction with the directional wattmeterdisclosed in US. Pat. No. 2,852,741, to J. R. Bird et al, entitledDirectional wattmeter and issued on Sept. 16, 1958.

One of the problems associated with directional couplers which aremachined as a cylindrical section of a transmission line is that themachining operations in the manufacture of these couplers are quiteexpensive because the component part must be manufactured to exactingspecifications in order to interlock with or threadably engage anadjacent component. Unless exacting specifications are maintainedbetween adjacent components, leakage between components may cause strayelectrical fields resulting in inaccuracies of measurement.

Another problem associated with these known directional couplers is theimportance of having the various inductive elements and capacitiveprobes precisely positioned in order to establish a predeterminedreactance or inductance with respect to the transmission line. Therequirement for exact positioning of these elements creates additionalproblems and increased man- 5 ufacturing cost.

SUMMARY OF THE INVENTION With the ever-increasing use of directionalcouplers as a single component in transmitting systems, as opposed tothe use of directional couplers as a major component of relativelyexpensive test equipment, it has been found to be highly desirable toprovide a directional coupler which may be manufactured at a substantialreduction in cost, as well as a directional coupler which may be massproduced with a high degree of reliability.

Also, transmitting systems are frequently subjected to greatermechanical shock than is normally encountered by test equipment. Thus,it has been found to be desirable to provide a directional coupler whichis rugged in construction and immune to damage as a result of normalmechanical shock.

The present invention is directed toward a directional coupler whichincorporates mechanical, as well as electrical features, for overcomingthe noted disadvantages, and others, of conventional coupler systems.

In accordance with the present invention, there is provided adirectional coupler for detecting unidirectional wave singles signals atransmission line. The coupler includes a housing member having atransmission line input connector and output connector mounted thereonand a ground plane partition member mounted within so as to define afirst and second chamber within the housing. The ground plane iselectrically bonded to the walls of the housing in order tosubstantially prevent the passage of electrical fields between the twochambers. One of the surfaces of an insulative board having securedthereon a layer of conductive material is attached to the partitionmember, and a layer of conductive material is secured to the othersurface of the insulative board so as to act as a primary transmissionconductor to define a predetermined impedance between the conductivelayer and the ground plane. In addition, a coupling element comprised ofanother layer of conductive material, is also secured to the insulativeboard in spaced relation with respect to the first conductive layer forreceiving a portion of the energy of a wave signal which is propagatedalong the primary transmission line.

The ground plane partition member and the conductive layer comprisingthe primary transmission line secured to the other side of theinsulative board are coupled between the input and output connectors soas to define a section of a transmission line, and the coupling elementis connected to an output circuit carried by the partition member at theside opposite to the insulative board to provide an output signal havinga value representative of a unidirectional wave signal on thetransmission line.

The primary transmission line or first conductive layer is comprised ofa thin film or strip of conductive material of a generally elongatedrectangular configuration, and includes a pair of L-shaped terminalmembers each having one leg portion electrically connected to one of theends of the elongated film of conductive material and another legportion connected to one terminal of one of the input connectors.

Thecoupling element is also comprised of a thin film of conductivematerial of a generally elongated rectangular configuration and issecured to the same face of the insulataive board as the firstconductive layer and in spaced parallel relationship with respectthereto.

Thus, the coupling element is capacitively coupled to Y Another objectof the present invention is the provision of a directional coupler whichis of rugged construction and immune to damage as a result of normalmechanical shock.

A further object of the present invention is to provide a directionalcoupler which may be produced at a substantial savings in manufacturingcosts.

Another object of the present invention is the provision of a directioncoupler having improved shielding between a radio frequency section ofthe coupler and electrical components in a signal measuring section ofthe coupler.

These and other objects and advantages of the invention will becomeapparent from the following description of a preferred embodiment of theinvention as read in conjunction with the accompanying drawings and inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view partlyin section illustrating a directional coupler embodying the presentinvention;

FIG. 2 is a top elevational view of the directional coupler asillustrated in FIG. 1, as viewed along the line 22;

FIG. 3 is a bottom elevational view of the directional couplerillustrated in FIG. 1, as viewed along the line 33;

FIG. 4 is a sectional view of the directional coupler illustrated inFIG. 2, as viewed along the line 44;

FIG. 5 is a sectional view of the directional coupler as illustrated inFIG. 1, as viewed along the line 55;

tional coupler of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT FIGS. 1 through 5 illustrate adirectional coupler in accordance with the present invention whichgenerally comprises a conductive rectangular housing member 10 having aninput coaxial connector 12 mountedon one end and an output coaxialconnector 14 mounted on the other end thereof. For purposes ofdiscussion, the coaxial connector 12 will be referred to as the inputconnector and coaxial connector 14 will be referred to as an outputconnector, however, it is to be understood that the circuitry in thedirectional coupler is symmetrical, and accordingly, the coupler may beconnected in a transmission line such that the coaxial connector 14serves as an input connector and the coaxial connector 12 serves as anoutput connector.

The outer conductors 16, 18 of the coaxial connectors 12, 14 areelectrically bonded to the end walls of the conductive housing member10, and the inner conductors 20, 22 of the connectors 12, 14 passthrough and are insulated from the end walls of the housing.

A ground'plane conductive partition member 24 is positioned within thehousing member 10 and is electrically bonded to four of the walls of thehousing so as to define an upper chamber 26 and a lower chamber 28. Thepartition member 24 serves as an electrical shield to preventradio-frequency fields which exist in the lower chamber 28 from passinginto the upper chamber 26 and adversely affecting the operation of thevoltage measuring circuitry in this chamber.

The partition member 24 is comprised of a generally rectangular platehaving a central portion 30 which extends in a horizontal plane, a pairof vertical portions 32, 34, and a pair of outer portions 36, 38 whichextend in a horizontal plane above the horizontal plane of the centralportion 30, as viewed in FIG. 1.

As illustrated in FIG. 1, partition member 24 is electrically andmechanically bonded to the end walls of the conductive housing 10through a pair of flange portions 40, 42, and is similarly bonded to theside wall of the housing member through the flange portions 44, 46, 48,50. The partition member 24 is also bonded to the opposite side wall ofthe housing member through the tab portions 52, 54, 56, as illustratedin FIG. 6, which extend through interlocking apertures in that wall.

An insulative board 58 which takes the form of a printed circuit boardis secured to the central portion 30 of the partition member 24 withthree rivets 61, 63, 64. The rivets extend through aligned apertures inthe central portion of the partition member 24 and the insulative board58.

Superimposed between a face of printed circuit board 58 and thepartition member 24 is a thin film of conductive material or layer 60which is secured to the insulative board by conventional printed circuittechniques. The primary line conductor 62 takes the form 'of strip layerof thin film conductive material which is similarly secured to anopposite face of the insulative board 58. The primary line conductorincludes an elongated rectangular central portion having a pair ofterminal strips 66, 68 extending from the ends thereof.

Electrical connection is made between the terminal strips 66, 68 and theconductors 20, 22 of the coaxial connectors 12, 14 through a pair ofgenerally L-shaped conductive bracket members 70, 72. The bracket member70 is secured to the terminal strip 66 of the primary line conductor 62and the insulative board 58 by a pair of rivets 74, 76. The rivets 74,76 extend through aligned apertures in one leg portion of the L- shapedbracket member 70, the terminal strip 66, and the insulative board 58.The inner conductor 20 of the coaxial connector 12 extends through anaperture 78 in the other leg portion of the bracket member 70 and iselectrically bonded to that leg portion at this aperture.

The bracket member 72 is similarly secured to the terminal strip 68 ofthe primary line conductor or strip.

layer 62 and the insulative board 58 by a pair of rivets 80, 82 whichextend through aligned apertures in one leg portion of the L-shapedbracket member 72, the terminal strip 68, and the insulative board 58.The inner conductor 22 of the coaxial connector 14 extends through anaperture 84 in the other leg portion of the bracket member 72 and iselectrically bonded to that leg portion at this aperture.

It will be noted that the rivets 74, 76, 80, and 82 do not engage orcontact the conductive layer 60.

The primary line conductor or strip layer 62 is of a configuration andis spaced from the thin film of conductive material 60 so as to define apredetermined characteristic impedance between the primary line 62 andthe thin film of conductive material 60. In view of the fact that thefilm of conductive material 60 is in direct electrical contact with thepartition member 24, the predetermined chacteristic impedance is alsomaintained between the primary line conductor 62 and the partitionmember 24.

A forward coupler 86 which takes the form of a generally rectangularthin film conductive strip is secured to an opposite face of theinsulative board from the conductive layer 60 in parallel spacedrelation with respect to the primary line conductor or layer 62.Similarly, a reverse coupler 88 which also takes the form of arectangular thin film conductive strip is secured to an opposite face ofthe insulative board from the conductive layer 60 and in parallel spacedrelation with respect to the primary line conductor, but on an oppositeside of the conductor from that of the forward coupler 86.

One of the leads of a diode 90 extends through an eyelet 92 of a discmica capacitor 94 and is electrically bonded to the eyelet 92 and to aterminal of the forward coupler 86. The other lead of the diode 90extends through an eyelet of another disc mica capacitor 96 and iselectrically bonded to the eyelet. The mica capacitor 96 includes aterminal connector 98 which is connected to and extends from the eyeletof this capacitor. The outer conductor of the capacitor 96 is connectedthrough a cylindrical shield 100 to the outer conductor of the capacitor94, and the outer conductor of the capacitor 94 is electrically bondedto the conductive layer 60 and is therefore in electrical contact withthe partition member 24. The shield 100 not only serves to electricallyconnect the outer conductor of the capacitor 94 and the capacitor 96 tothe plate 60, but this shield also serves as a secondary shield for thediode 90 to prevent radio frequency fields which exist in the lowerchamber 28 from adversely affecting the operation of the diode.

One of the leads of a resistor 102 is connected to the other terminal ofthe forward coupler 86 and the other lead of this resistor is connectedto a cylindrical shield 104 which is in turn bonded to the conductivelayer 60. The terminal 98 of the mica capacitor 96 is connected througha resistor 106 to a forward output terminal 108, and a capacitor 110 isconnected between the forward output terminal 108 and the conductivehousing member 10.

Similarly, one of the leads of a diode 112 extends through an eyelet 114of a disc mica capacitor 116 and is electrically bonded to the eyelet 114 and to a terminal of the reverse coupler 88. The other lead of thediode 112 extends through the eyelet in another disc mica capacitor 118and is electrically bonded to the eyelet. The mica capacitor 1 18includes a terminal connector 1 19 which is connected to and extendsfrom the eyelet of this capacitor. The outer conductor of the capacitor118 is connected through a cylindrical shield 120 to the outer conductorof the capacitor 116, which is in turn electrically bonded to theconductive plate 60. Thus, the cylindrical shield 120 serves to connectthe outer conductor of the capacitors 116, 118 as well as to provide asecondary shield for the diode 112.

One of the leads of a resistor 122 is connected to the other terminal ofthe reverse coupler 88 and the other lead of this resistor is connectedto a shield 124 which is grounded to the conductive plate 60. Inaddition, the center terminal 120 of the mica capacitor. 118 isconnected through a resistor 126 to a reverse output termi-,

nal 128. A capacitor 130 is then coupled between the reverse outputterminal 128 and the conductive housing member 10.

As illustrated, the forward coupler 86 includes a variable capacitivebalance tab 132. The balance tab 132 takes the form of a thin aperturedrectangular plate. The lead of the resistor which is bonded to theterminal of the forward coupler 86 extends through an aperture in theterminal, through an aperture in a spacer bushing 133, and through theaperture in the balance tab 132. The balance tab 132 is bonded to theresistor lead at the aperature and is positioned to overlay in a spacedrelation to the primary conductive line 62. Thus, the balance tab 132may be bent slightly toward or away from the primary line conductor orstrip layer 62, or the tab may be rotated about the resistor lead tovary the amount of capacitive coupling between the forward coupler 86and the primary line conductor or strip layer 62. A similar balance tab134 and spacer bushing 135 are bonded to a lead of the resistor 122 at aterminal of the reverse coupler 88.

Reference is now made to FIG. 7 which illustrates in more detail theelectrical circuitry of the directional coupler. For purposes ofdiscussion, reference will be made to lumped impedances as opposed to adetailed consideration of the distributed parameters in the circult.

As previously discussed, one of the terminals of the forward coupler 86is connected through a resistor 102 to a common ground point. The otherterminal of this coupler is connected to one of the terminals of aninductance L which represents the distributed inductance in thesecondary circuit. The other terminal of the inductance L is connectedto one terminal of a capacitor 94, and the other terminal of thiscapacitor is connected to ground and to the anode of a diode 90. Thecathode of the diode 90 is connected through a capacitor 96 to ground,and the cathode of this diode is also connected through a resistor 106to the forward output terminal 108. The capacitor 110 is connecteddirectly between the forward output terminal and ground.

A mutual impedance M exists between the strip layer 62 and the forwardcoupler 86. This mutual impedance is a result of a magnetic field whichsurrounds the strip layer 62 and intercepts the forward coupler 86 tothereby induce a current in this coupler. A similar current is inducedin the strip layer 62 as a result of a magnetic field which surroundsthe forward coupler 86. Thus, this mutual coupling or inductance isillustrated as the lumped mutual inductance M. The capacitive couplingbetween the strip layer 62 and the forward coupler 86 is represented bythe lumped capacitance C.,. As discussed previously, this couplingcapacitance may be varied by changing the position of the capacitancebalance tab 132 with respect to the strip layer 62.

One of the terminals of the reverse coupler 88 is connected through theresistor 122 to ground and the other terminal of this coupler isconnected to one of the terminals of a secondary inductance L. The otherterminal of the inductance L is connected to one terminal of a capacitor116, and the other terminal of this capacitor is connected to ground andto the anode of the diode 112. The cathode of the diode 112 is connectedto one terminal of a capacitor 118 and the other terminal of thiscapacitor is connected to ground and through a resistor 126 to thereverse output terminal 128. The reverse output terminal 128 is alsoconnected through a capacitor 130 to ground.

As in the case of the forward directional circuit, a mutual inductanceexists between the primary line conductor or strip layer and thesecondary circuit which is represented by the lumped mutual inductanceM. The capacitive coupling between the primary line conductor and thereverse coupler is indicated as a lumped capacitance C 1 The operationof the forward coupling circuit is substantially similar to that of thereverse coupling circuit. Thus, only the forward circuit will beconsidered for purposes of discussion. 7

With a radio frequency signal applied through the directional coupler, aportion of the wave energy in the primary line is transferred from theprimary line conductor 62 to the forward coupler 86. The wave energyapplied to the forward coupler represents both the forward and reflectedtraveling wave energy transmitted through the primary line conductor.

The coupler 86 is connected to ground through the resistor 102 andthrough the inductance L and the capacitor 94. Thus, a current signalinduced in coupler 86 is caused to flow from the coupler 86 to ground.This current signal developed across the capacitor 94 is applied to apeak voltmeter comprised of the capacitors 96, 110, the diode 90 and theresistor 106. Accordingly, the current signal on the capacitor 94 isapplied to the input capacitor 96 through the diode 90 to thereby causethis capacitor to charge to a voltage equal to the peak voltage of thesignal appearing across the capacitor 94. The peak voltage developedacross the capacitor 96 is then applied through the resistor 106 to theforward output terminal 108. The capacitor 110 serves primarily as afiltering capacitor for the output signal.

With a direct-current voltmeter G connected between the forward outputterminal 108 and ground, it is possible to measure the direct currentoutput signal developed by the forward circuitry in order to determinethe value of a forward wave signal propagated along the transmissionline.

6 With traveling wave energy transmitted through the directional couplerfrom left to right as viewed in FIG. 1, the capacitive balance tab 132is adjusted so that the voltage which is developed across C which is afunction of the primary line voltage, is made equal to the voltagedeveloped across capacitor 94, which is a function of line current.Thus, there will be a 180 degree phase difference at capacitor 94 in thetwo like magnitude signals, voltage will be approximately zero volts,thereby producing a reading of zero volts on voltmeter With travelingwave energy transmitted from right to left through the coupler as viewedin FIG. 1, the voltage across the capacitor 94 is a function of theprimary line voltage and approximates the voltage coupled from theprimary line through the mutual impedance M, lumped inductance L, theresistor 102, and the capacitor 94. The phase relation of these voltagesignals is equal to zero. Accordingly, the circuit supplies a voltageacross the capacitor 94 to thereby provide a direct current signal whichis applied through the network including the diode 90, the capacitor 96,the resistor 106, and the capacitor to the voltmeter G.

In other words, if a radio frequency signal is transmitted in onedirection only through a transmission line of impedance Z the linecurrent I will be equal to a voltage E divided by the characteristicimpedance Z, of the line. If the line voltage and current are assumed tobe in a zero angular relation with respect to each other, the voltageand current will be at a degree phase relationship with respect to eachother for a signal traveling in the opposite direction. At a givenfrequency, the reactance X across the lumped impedance L, and thereactance X across the capacitor 94 become equal to each other. Also,the reactance X across the capacitance C, is relatively large withrespect to the reactance X across the impedance L and the reactance Xacross the capacitor 94.

Thus, a current flowing through the inductance L and the capacitor 94 asa result of this line voltage may be defined as E or the line voltagedivided by the reactance X If the reactance X is small relative to thereactance X the ratio of the voltage across the capacitor 94 to the linevoltage will be approximately equal to the ratio of the capacitor C tothe capacitance 94.

Thus, assuming that the capacitance C, is very small in comparison tothe capacitance C across the capacitor 94, and that the capacitance C isvery large in comparison to the resistance R, of the resistor 102, and

that the inductance L is very small in comparison to the resistance R,of resistor 102, the above relationships give rise to the followingequation:

At a frequency where the reactance X of the inductor L is equal to thereactance X of the capacitor 94, the voltage across the capacitor 94 maybe represented by the following equation:

E Ml/R, c

where E equals the voltage across the capacitor 94, M equals theimpedance of the mutual inductor M, and I equals the current passingthrough the capacitor 94. The equations (3) and (4) are essentiallycorrect assuming that the capacitance C is large in comparison to theresistance R across the resistor 102 and that the inductance L is smallin comparison to the resistance R of the resistor 102. Again, it shouldbe noted that the j and m in equation (3) do not appear in equation (4)thereby indicating that there is no phase shift and that the circuit isnot responsive to change in frequency.

In view of the fact that equations (3) and (4) include no phase shiftfactors or frequency factors, and in view of the fact that the voltageand current in a transmission line for a given single direction of wavetransmission are defined by the characteristic impedance Z and that thevoltage and current on the line are related angularly as either zero or180 degrees dependent upon the direction of inspection, it is possibleto combine the voltage and current coupling. Thus, the voltage E acrossthe capacitor 94 is of equal magnitude for equal line voltages andcurrents for a given transmission line at a given characteristicimpedance Z Accordingly, by subtracting equation (3) from equation (2),the following equation is derived:

E94 E94 =(C4/C94) (E1)+(MI/R1C94) Thus, for a wave propagated in a givendirection, the voltage across the capacitor is equal to zero indicatingthat the circuit achieves the desired directivity.

The equation (5) may be rewritten as follows:

Thus, equation (8) sets forth the relationship of component values whichprovide a frequency independent solution to the computation of componentvalues for achieving directivity. Accordingly, the values of thecoupling components may be computed from equation (8) in order toachieve directivity.

Although the invention has been described in connection with a preferredembodiment, it will be readily apparent to those skilled in the art thatvarious changes in form and arrangement of parts may be made to suitrequirements without departing from the spirit and scope of the appendedclaims.

Having thus described my invention I claim:

1. A directional coupler for detecting and measuring undirectional flowof power in a transmission line comprising an elongated housing ofconductive material having a transmission line input and outputconnectors mounted thereon,

a partition member of conductive material positioned within said housingto define a first and a second chamber for substantially preventing thepassage of electrical fields from said first chamber to said secondchamber,

an insulative board having first and second oppositely facing surfaces,

a first film layer of conductive material secured to said first surfaceof said insulative board, said board secured to at least a portion ofsaid partition member with said first film layer sandwichedtherebetween,

a second film layer of conductive material secured to at least a portionof said second surface of said insulative board thereby defining apredetermined impedance between said first and second film layers,

a third film layer of conductive material having first and secondterminal ends and secured to at least a portion of said second surfaceof said board in spaced relation with respect to said second film layerthereby defining a predetermined impedance between said second and thirdfilm layers,

said transmission line input and output connectors respectively havingone terminal coupled to said first film layer and its other terminalcoupled to said partition member,

a signal developing network mounted on the side of said partition memberopposite said insulative board and coupled to said first and third filmlayers to develop an output signal representative of the unidirectionalline voltage of the signal propagated along the transmission line for agiven line characteristic impedance, and

indicator means connected to receive said output signal for producing avisual presentation representative of the value of said output signal.

2. A directional coupler used for detecting and measuring unidirectionalflow of power in a transmission line comprising an elongated hollowmetallic housing,

a transmission line input and output terminal at the ends of saidhousing with each terminal providing a means for connection to theprimary and secondary conductors of a transmission line,

a partition member for the full length of said housing and secured tosides and ends thereof forming two separate chambers therein forsubstantially preventing the passage of electrical fields between saidchambers,

the respective ends of said partition members secured to said terminalsecondary connection means,

an insulative board secured to a portion of one face of said partitionmember in one of said chambers,

said board having a first conductive layer secured to one face of saidboard and in electrical contact with said partition member,

a first elongated strip layer secured to the opposite face of said boardfrom said first layer with its opposite ends connected to said terminalprimary connection means,

said insulative board and said layers forming a predetermined impedancecoupling,

a second elongated strip layer secured to said board opposite face andpositioned in juxtaposed relation to said first elongated strip layer,

a signal developing and measuring network mounted on theother face ofsaid partition member in the other of said chambers and electricallycoupled to both said first conductive layer and said second elongatedstrip layer to develop an output signal representative of theunidirectional line voltage of the signal propagated along thetransmission line for a given line characteristic impedance and producea visual representation thereof.

3. The coupler of claim 2 characterized in that said partition membercomprises a central portion and a pair of end portions, said endportions in a plane parallel to said central portion, said end portionssecured to the ends of said housing, said network mounted on the topface of said central portion and said insulative boardwith saidconductive layers mounted on the bottom face of said central portion; v

4. The coupler of claim 3 characterized in that each of said terminalprimary connection means includes a mounting bracket positioned in thespace provided below one of said end portions to connect an end of saidfirst strip layer to one of said terminals.

5. The coupler of claim 2 characterized by resistive and diode rectifiermeans included in said signal developing and measuring network andshield means surrounding said resistive and diode rectifier means forfurther isolating said resistive and rectifier means from strayelectrical fields.

6. The coupler of claim 2 characterized by a third elongated strip layersecured to said board opposite face and positioned in juxtaposedrelation to said first conductive layer opposite to said second striplayer, and

a second signal developing network also mounted on the other face ofsaid partition member and electrically coupled to both said firstconductive layer and said third elongated strip layer to develop asecond output signal representative of the unidirectional line voltageof said propagated signal in a direction opposite to that developed inconnection with said second strip layer.

UNITED STATES PATENT OFFICE 569 CERTIFICATE OF CORRECTION Patent No. 3829 770 Dated August 13 I 1974 Inventor) Harold E. Stevens It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 6, line 20, change "l20' to --ll9--;

Column 8, line 1, change "C to capacitor 94-;

Column 9, line 6, in the formula, change "C to .-C

Column 9, line 10, in the formula, change "C to --C 4;

Claim 1, column 10, line 12, delete "a" Claim 1, column 10, line 40,change "first" to second- Claim 2, column 10, line 56, before"transmission" delete ag and, change "terminal" to -terminals- Claim 2,column 10, line 66, change "members" to member-;

Claim 6, column 12, line 18 change "conductive" to elongated strip and,change "second strip" to second elongated str1p-.

Signed and Scalcd this ninth Day of December 1975 0 '[SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Patentsand Trademarks Q

1. A directional coupler for detecting and measuring undirectional flowof power in a transmission line comprising an elongated housing ofconductive material having a transmission line input and outputconnectors mounted thereon, a partition member of conductive materialpositioned within said housing to define a first and a second chamberfor substantially preventing the passage of electrical fields from saidfirst chamber to said second chamber, an insulative board having firstand second oppositely facing surfaces, a first film layer of conductivematerial secured to said first surface of said insulative board, saidboard secured to at least a portion of said partition member with saidfirst film layer sandwiched therebetween, a second film layer ofconductive material secured to at least a portion of said second surfaceof said insulative board thereby defining a predetermined impedancebetween said first and second film layers, a third film layer ofconductive material having first and second terminal ends and secured toat least a portion of said second surface of said board in spacedrelation with respect to said second film layer thereby defining apredetermined impedance between said second and third film layers, saidtransmission line input and output connectors respectively having oneterminal coupled to said first film layer and its other terminal coupledto said partition member, a signal developing network mounted on theside of said partition member opposite said insulative board and coupledto said first and third film layers to develop an output signalrepresentative of the unidirectional line voltage of the signalpropagated along the transmission line for a given line characteristicimpedance, and indicator means connected to receive said output signalfor producing a visual presentation representative of the value of saidoutput signal.
 2. A directional coupler used for detecting and measuringunidirectional flow of power in a transmission line comprising anelongated hollow metallic housing, a transmission line input and outputterminal at the ends of said housing with each terminal providing ameans for connection to the primary and secondary conductors of atransmission line, a partition member for the full length of saidhousing and secured to sides and ends thereof forming two separatechambers therein for substantially preventing the passage of electricalfields between said chambers, the respective ends of said partitionmembers secured to said terminal secondary connection means, aninsulative board secured to a portion of one face of said partitionmember in one of said chambers, said board having a first conductivelayer secured to one face of said board and in electrical contact withsaid partition member, a first elongated strip layer secured to theopposite face of said board from said first layer with its opposite endsconnected to said terminal primary connection means, said insulativeboard and said layers forming a predetermined impedance coupling, asecond elongated strip layer secured to said board opposite face andpositioned in juxtaposed relation to said first elongated strip layer, asignal developing and measuring network mounted on the other face ofsaid partition member in the other of said chambers and electricallycoupled to both said first conductive layer and said second elongatedstrip layer to develop an output signal representative of theunidirectional line voltage of the signal propagated along thetransmission line for a given line characteristic impedance and producea visual representation thereof.
 3. The coupler of claim 2 characterizedin that said partition member comprises a central portion and a pair ofend portions, said end portions in a plane parallel to said centralportion, said end portions secured to the ends of said housiNg, saidnetwork mounted on the top face of said central portion and saidinsulative board with said conductive layers mounted on the bottom faceof said central portion.
 4. The coupler of claim 3 characterized in thateach of said terminal primary connection means includes a mountingbracket positioned in the space provided below one of said end portionsto connect an end of said first strip layer to one of said terminals. 5.The coupler of claim 2 characterized by resistive and diode rectifiermeans included in said signal developing and measuring network andshield means surrounding said resistive and diode rectifier means forfurther isolating said resistive and rectifier means from strayelectrical fields.
 6. The coupler of claim 2 characterized by a thirdelongated strip layer secured to said board opposite face and positionedin juxtaposed relation to said first conductive layer opposite to saidsecond strip layer, and a second signal developing network also mountedon the other face of said partition member and electrically coupled toboth said first conductive layer and said third elongated strip layer todevelop a second output signal representative of the unidirectional linevoltage of said propagated signal in a direction opposite to thatdeveloped in connection with said second strip layer.